The basic purpose of this ongoing research is to demonstrate the sensory mechanisms underlying visual orientation. A wide range of techniques have been applied in this study ranging from microspectrophotometry to electron microscopy, experimental cytology, electrophysiology as well as behavior in the field and in the laboratory. A major point of interest remains the visual significance of polarized light. During the current year our attention has been focussed on the stability and turnover of the photoreceptor membrane studied by freeze fracture, freeze-etch and transmission electron microscopy. At the other end of the hierarchy we have also begun using a closed circuit TV system to record visual behavior and an electronic scanning device (the "bug watcher") which samples and digitizes the orientation patterns for computer analysis. Direct demonstration of photoreceptor membrane uptake in pinocytotic vesicles is an important priority. Ruthenium red labeling of membrane is under current test; failure to find tracer in the intercellular spaces of the rhabdom has plagued this work until now so that progress is difficult to predict. Comparative freeze and TEM study of R8 is an important item on the agenda. Comparison of the CNS connections of this cell in relation to differences in photoreceptor membrane are particularly interesting to us. A closed circuit video system and the servocontrol for regulating e-vector direction and oscillation are now complete and in operation. Oriented visual responses have been recorded for several species of fish and crustaceans. Currently the bug watcher's capacity to digitize the behavior is being tested and when sufficient data has been accumulated computer analysis of chi square and other appropriate estimates of performance will be made. We anticipate that the detailed quantitative information this approach is designed to yield will provide insight into the mechanism of visual information processing and its relation to visually oriented behavior.